Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

When David poses as Goliath

10.01.2020

A stripped helium star solves the massive black hole mystery

Stellar black holes form when massive stars end their life in a dramatic collapse. Observations have shown that stellar black holes typically have masses of about ten times that of the Sun, in accordance with the theory of stellar evolution.


A black hole

Image: FAU

Recently, a Chinese team of astronomers claimed to have discovered a black hole as massive as 70 solar masses, which, if confirmed, would severely challenge the current view of stellar evolution.

The publication immediately triggered theoretical investigations as well as additional observations by other astrophysicists. Among those to take a closer look at the object was a team of astronomers from the Universities of Erlangen-Nürnberg and Potsdam.

They discovered that it may not necessarily be a black hole at all, but possibly a massive neutron star or even an ‘ordinary’ star. Their results have now been published as a highlight-paper in the renowned journal ‘Astronomy & Astrophysics’ *.

The putative black hole was detected indirectly from the motion of a bright companion star, orbiting an invisible compact object over a period of about 80 days. From new observations, a Belgian team showed that the original measurements were misinterpreted and that the mass of the black hole is, in fact, very uncertain.

The most important question, namely how the observed binary system was created, remains unanswered. A crucial aspect is the mass of the visible companion, the hot star LS V+22 25. The more massive this star is, the more massive the black hole has to be to induce the observed motion of the bright star. The latter was considered to be a normal star, eight times more massive than the Sun.

A team of astronomers from Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the University of Potsdam had a closer look at the archival spectrum of LS V+22 25, taken by the Keck telescope at Mauna Kea, Hawaii.

In particular, they were interested in studying the abundances of the chemical elements on the stellar surface. Interestingly, they detected deviations in the abundances of helium, carbon, nitrogen, and oxygen compared to the standard composition of a young massive star.

The observed pattern on the surface showed ashes resulting from the nuclear fusion of hydrogen, a process that only happens deep in the core of young stars and would not be expected to be detected at its surface.

‘At first glance, the spectrum did indeed look like one from a young massive star. However, several properties appeared rather suspicious. This motivated us to have a fresh look at the archival data,’ said Andreas Irrgang, the leading scientist of this study and a member of the Dr. Karl Remeis-Observatory in Bamberg, the Astronomical Institute of FAU.

The authors concluded that LS V+22 25 must have interacted with its compact companion in the past. During this episode of mass-transfer, the outer layers of the star were removed and now the stripped helium core is visible, enriched with the ashes from the burning of hydrogen.

However, stripped helium stars are much lighter than their normal counterparts. Combining their results with recent distance measurements from the Gaia space telescope, the authors determined a most likely stellar mass of only 1.1 (with an uncertainty of +/-0.5) times that of the Sun.

This yields a minimum mass of only 2-3 solar masses for the compact companion, suggesting that it may not necessarily be a black hole at all, but possibly a massive neutron star or even an ‘ordinary’ star.

The star LS V+22 25 has become famous for possibly having a massive black hole companion. However, a closer look at the star itself reveals that it is a very intriguing object in its own right, as whilst stripped helium stars of intermediate mass have been predicted in theory, only very few have been discovered so far. They are key objects to understanding binary star interactions.

* doi: https://doi.org/10.1051/0004-6361/201937343

Further information:
Dr. Andreas Irrgang
Phone: +49 951 9522216
andreas.irrgang@fau.de

Wissenschaftliche Ansprechpartner:

Dr. Andreas Irrgang
Phone: +49 951 9522216
andreas.irrgang@fau.de

Originalpublikation:

https://doi.org/10.1051/0004-6361/201937343

Dr. Susanne Langer | idw - Informationsdienst Wissenschaft
Further information:
https://www.fau.eu/2020/01/10/news/research/when-david-poses-as-goliath/

More articles from Physics and Astronomy:

nachricht Laserphysics: At the pulse of a light wave
13.01.2020 | Ludwig-Maximilians-Universität München

nachricht Explosion or collapse?
13.01.2020 | Helmholtz Association

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: World Premiere in Zurich: Machine keeps human livers alive for one week outside of the body

Researchers from the University Hospital Zurich, ETH Zurich, Wyss Zurich and the University of Zurich have developed a machine that repairs injured human livers and keep them alive outside the body for one week. This breakthrough may increase the number of available organs for transplantation saving many lives of patients with severe liver diseases or cancer.

Until now, livers could be stored safely outside the body for only a few hours. With the novel perfusion technology, livers - and even injured livers - can now...

Im Focus: SuperTIGER on its second prowl -- 130,000 feet above Antarctica

A balloon-borne scientific instrument designed to study the origin of cosmic rays is taking its second turn high above the continent of Antarctica three and a half weeks after its launch.

SuperTIGER (Super Trans-Iron Galactic Element Recorder) is designed to measure the rare, heavy elements in cosmic rays that hold clues about their origins...

Im Focus: LZH’s MOMA laser ready for the flight to Mars

One last time on Earth it has been turned on in France in December 2019. The next time the MOMA laser developed by the Laser Zentrum Hannover e.V. (LZH) is going into operation will be on Mars. The ExoMars rover into which the laser is integrated has now successfully passed the thermal vacuum tests at Airbus in Toulouse, France.

For 18 days the ExoMars rover Rosalind Franklin was subjected to thermal vacuum tests at Airbus. There, it had to withstand strong changes in temperature and...

Im Focus: Atacama Desert: A newly discovered biocoenosis of lichens, fungi and algae shapes entire landscapes

The Atacama Desert in Chile is the oldest and most arid desert on earth. Organisms living in this area have adapted to the extreme conditions over thousands of years. A research team led by Dr Patrick Jung has now discovered and investigated a previously unknown biocoenosis of lichens, fungi, cyanobacteria and algae. It colonises tiny stones, so-called grit and its need for water is satisfied by fog and dew. These organisms also decompose the rock on and in which they live. The scientists believe that this is how they have shaped the landscape of the Atacama Desert. Their study was published in the renowned scientific journal "Gebiology".

Many desert areas have large black spots in the sand. These spots are mineral deposits, so-called desert varnish. In the Atacama Desert, which can be compared...

Im Focus: Nano antennas for data transfer

For the first time, physicists from the University of Würzburg have successfully converted electrical signals into photons and radiated them in specific directions using a low-footprint optical antenna that is only 800 nanometres in size.

Directional antennas convert electrical signals to radio waves and emit them in a particular direction, allowing increased performance and reduced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

„Advanced Battery Power“- Conference, Contributions are welcome!

07.01.2020 | Event News

International Coral Reef Symposium 2020 Holds Photo Competition

19.12.2019 | Event News

The Future of Work

03.12.2019 | Event News

 
Latest News

Scientists in Mainz develop a more sustainable photochemistry

14.01.2020 | Life Sciences

Laserphysics: At the pulse of a light wave

13.01.2020 | Physics and Astronomy

New function for potential tumor suppressor in brain development

13.01.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>